This invention relates to load cells and to scales and other apparatus utilizing load cells.
One type of load cell includes a load-receiving member connected by a pair of spaced bands to a support member, the ends of each band being connected in a cantilever fashion to its respective member. A strain gauge connected to any of the bands, undergoes a change in resistance proportional to deflection of the band and therefore proportional to the load applied to the load-receiving member. A Wheatstone bridge or other resistance measuring device connected to the strain gauge can accurately indicate the load on the load cell. If care is taken to apply the load along the axis of the load-receiving member, such scales can provide accuracies of well within 0.1% of full scale, which is often used as a criteria by government agencies in certifying the scale for commercial use. However, if the load is applied even a small distance away from the axis of the load-receiving member, then the accuracy of the scale greatly decreases. For example, a load cell may have a linearity of 0.05% of full scale for on-center loads, but the linearity may decrease to 0.25% for loads applied at an angle of 3.degree. with respect to the axis of the load-receiving member. Linkages have been utilized to assure on-axis loading of load cells, but these linkages are relatively expensive and add considerably to the cost and complexity of scales that utilize load cells. A load cell of high accuracy, which was largely insensitive to off-axis loading, would permit the construction of scales and other load-measuring instruments at a significantly lower cost.